1. Field of the Invention
This invention relates to an element for detecting bad smell gas, alcoholic gas, and humidity in the surrounding atmosphere.
2. Description of Prior Arts
There have so far been used various materials for the humidity detecting element, such as metal oxides, inorganic and organic electrolytes, and those substances utilizing the relative humidity dependent property of the electric conductivity of an organic substance dispersed in an electrically conductive material. Use of such materials has been considered from the standpoint of readiness in handling the element and its connectivity with a micro-processor. Of these various materials, the metal oxides are particularly preferred on account of their stability in operation and heat-resistance.
Measurement of concentration of methyl mercaptan (CH.sub.3 SH), hydrogen sulfide (H.sub.2 S) and others which are principal constituents of offensive odor to occur at the sewage disposing sites, refuse disposing sites, and so forth has so far been done in part by electro-chemical expedients. However, such electro-chemical processings require sampling of the gas and make the measuring operations complicated. On the other hand, conventional semiconductor gas sensors are not sufficient in their sensitivity and so have not yet found their way to the practical utilization.
For the element to detect alcoholic gas, there have also been used various kinds of material such as those utilizing variations in electrical conductivity of a metal oxide semiconductor due to their chemical adsorption of the gas. Such use is also from the standpoint of readiness in handling the element and its compatibility with a micro-processor. The material for constituting the element is selected from SnO.sub.2, ZnO, and others. However, since these materials have almost same degree of sensitivity to various inflammable gases, the selective detection of alcoholic gas has been difficult.
Further, there has heretofore been no element in a single integral construction which is capable of detecting both humidity and gas, and yet has a stable humidity sensing characteristic and a gas sensing characteristic having a quick response speed with high sensitivity and high selectivity to those bad smell gases and alcoholic gas.